1. Field of the Invention
The present invention relates to a memory structure and a fabricating method thereof. More particularly, the present invention relates to an illuminating efficiency-increasable and light-erasable embedded memory structure and a fabricating method thereof.
2. Description of Related Art
A memory is a semiconductor device used for storing data or information. The requirement for the memory is getting higher and higher along with the advancement in the function of computer micro-processors and the increase in volume of software programs and calculations. The technique and the process for fabricating memory devices with large-volume and low-cost memory have been driving the semiconductor technology to go towards high integration constantly.
Among various memory products, a non-volatile memory has been applied widely to personal computers and other electronic equipments in which data can be read from, written to, or erased from the non-volatile memory repeatedly and the data stored in the non-volatile memory will not be lost after power off.
FIG. 1 is a cross-sectional view of a conventional single poly non-volatile memory structure.
Referring to FIG. 1, a memory device 102 is disposed on a substrate 100. The memory device 102 includes two metal oxide semiconductor (MOS) transistors 104 and 106 disposed adjacently on the substrate 100, and the gates of the MOS transistors 104 and 106 are respectively used as a select gate 108 and a floating gate 110 of the memory device 102. While programming the memory device 102, charges are stored in the floating gate 110. While erasing the data stored in the memory device 102, conventionally, the floating gate 110 is radiated with a UV light so that the charges stored in the floating gate 110 can be erased.
If the memory device 102 is an embedded memory, a metal interconnect structure covers the memory device 102. In a metal interconnect structure adopting a copper process, the metal interconnect is composed of a plurality of copper metal layers formed in a plurality of dielectric layers, and a silicon nitride layer is formed on each dielectric layer as a cap layer for protecting the copper metal layer.
However, the dielectric layers and the silicon nitride layers absorb the UV light, and the UV light has very low transmittance in the silicon nitride layers. Therefore, while erasing the data stored in the memory device 102, the UV light cannot penetrate the dielectric layers and the silicon nitride layers in the metal interconnect structure effectively in order to radiate the floating gate 110, and accordingly the data stored in the floating gate 110 cannot be erased effectively by the UV light.